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COMMON PART

Project Number23-22-00270

Project titleSource of extreme ultraviolet radiation based on a discharge supported by radiation from a gyrotron of submegawatt power level in a gas flow

Project LeadAbramov Ilya

AffiliationFederal Research Center Institute of Applied Physics of the Russian Academy of Sciences,

Research area 02 - PHYSICS AND SPACE SCIENCES, 02-502 - Low-temperature plasma

Keywordsplasma with multiply charged ions, gas discharge, plasma fluid dynamics, interaction of radiation with matter

PROJECT CONTENT

Annotation
The objective of the project is to develop the theoretical basis of a source of radiation of extreme ultraviolet (EUV) wavelength range intended for projection lithography, based on a steady state electron-cyclotron resonant (ECR) discharge with multiply charged ions, supported by gyrotron radiation in a gas flow. Noble gases or metal vapors can be used as a working substance. The proposed source is the synthesis of two promising technologies: the generation of high-power sub-terahertz radiation using modern gyrotrons and the generation of highly charged ions using ECR plasma heating in an open magnetic trap. Both technologies are know-how of the Institute of Applied Physics of the Russian Academy of Sciences. The scientific novelty of the proposed research is, first of all, in their joint application, designed to solve the main problem of EUV radiation sources based on the ECR discharge: to ensure the possibility of localization of the radiating region (point-like source) simultaneously with high values of the coefficient of absorption of microwave radiation supporting plasma. The solution to this problem will make it possible to use radiation with a significantly higher average power to maintain the plasma compared to commonly used sources of EUV radiation based on laser produced plasma, which means that it will allow one to expect significantly higher values of the average power of the generated EUV radiation. As a source of EUV radiation, a discharge is proposed in which a flow of dense (up to 10^19 cm^(-3)) working substance will propagate from a nozzle located in the center of the coil of a strong electromagnet, which ensures the fulfillment of ECR conditions with sub-terahertz radiation of a gyrotron. Limitation of the flow expansion due to the transverse confinement of the plasma by an external magnetic field will make it possible to maintain the subsonic flow, in which, in contrast to the supersonic one, where a significant part of the power absorbed by the discharge is used to accelerate the flow, the main loss channel will be successive multiple ionization by electron impact and line radiation of multiply charged ions. In the region of ECR heating electrons can acquire energies of several hundred electronvolts, which are comparable to the ionization potentials of highly charged ions, whose spectra contain lines of the target EUV range. The high density of the plasma flow will allow volume losses to ensure a fairly rapid drop in the average electron energy from the heating region, thereby providing thermal insulation of the discharge. The development of the theoretical basis of the proposed method of EUV-light generation will include a description of the three most important aspects for its operation: the fluid dynamics of a dense plasma flow with multiply charged ions, the transfer of radiation of the line spectrum of multiply charged ions in the plasma volume, and the electrodynamics of the absorption of subterahertz radiation by a plasma flow. The research will be based to a large extent on the existing scientific background of the team.

Expected results
1. A fluid model of a steady state strongly radiating flow of a dense plasma with multiply charged ions under conditions of a localized resonant energy input will be developed. 2. A model will be developed for the absorption of electromagnetic radiation in the subterahertz frequency range by a flow of dense magnetized plasma under ECR conditions. 3. Optimal from the point of view of EUV radiation generation, the combustion regimes of a stationary ECR discharge with multiply charged ions, supported by the radiation of modern gyrotrons of a submegawatt power level in a gas flow, will be found, and conclusions about the prospects of the proposed concept of the EUV radiation source will be drawn. The theory developed within the project will make it possible to advance in understanding the physics of discharges maintained in gas flows by high-power radiation in the subterahertz frequency range. On its basis, a search will be made for optimal combustion modes from the point of view of EUV radiation generation of a stationary ECR discharge with multiply charged ions, supported by the radiation of modern gyrotrons of a submegawatt power level in a flow of noble gases and metal vapors, and conclusions about the prospects of the proposed concept of an EUV radiation source will be made. The success of the exploratory part of the project may become a stimulus for the translation of the proposed fundamental research into practice in the future, and the developed theory can become the basis for the preparation of a proof-of-principle experiment.

REPORTS